A large volume of organic solvents (e.g., an absorbable material, a volatile organic compound) such as NMP (N-methyl-pyrrolidone) are discharged during a process of manufacturing a secondary battery such as a lithium ion battery. Accordingly, it is desirable to develop a technology to recover the organic solvents.
Note that in a negative electrode slurry used to form a negative electrode, for example, NMP is used as a solvent (i.e., a mixed solvent) to dissolve a negative electrode conductive agent (e.g., carbon) and polyvinylidene difluoride (PVDF) as a binder.
Next, the negative electrode slurry containing NMP as a mixed solvent is applied on an electrode plate. Then, the plate is dried with a hot air drier. Accordingly, the NMP is vaporized in hot air during the drying. After that, exhaust gas containing vaporized NMP is discharged.
It is important to separate and recover the organic solvents, such as NMP included in such exhaust gas, from the exhaust gas. The applicant of the present application has disclosed various technologies for their separation and recovery (see JP2010-201282A).